Group 7 Halogens

• as the atomic number of the halogens increases, the elements have a darker colour and higher boiling point
• At room temperature:

  • chlorine (Cl2) is a fairly reactive, poisonous, green gas
  • Bromine (Br2) is a poisonous, red-brown liquid, which gives off an orange vapour at room temperature
  • Iodine (I2) is a dark grey crystalline solid which gives off a purple vapour when heated
• Displacement Reactions


  A reaction where a more reactive element displaces a less reactive element from a compound
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• More Reactive Halogens


  Will Displace Less Reactive Ones
• Displacement Reaction


  1. A more reactive element reacts with a compound

  2. Displaces a less reactive element from the compound
• Displacement Reaction


  1. Chlorine reacts with potassium iodide

  2. Chlorine displaces iodide ion

  3. Forming potassium chloride
• Halogens in Group 7

  • Fluorine
  • Chlorine
  • Bromine
  • Iodine
  • Astatine
• Properties of halogens


  • Reactivity decreases down the group
  • Melting and boiling points increase down the group
  • Colour gets darker down the group
• Oxidation

  Loss of electrons
• Reduction


  Gain of electrons
• Halogen Displacement Reactions


  1. Involve transfer of electrons

  2. Oxidation and reduction happen simultaneously
• An oxidising agent accepts electrons and gets reduced
• A reducing agent donates electrons and gets oxidised
• Redox reactions


  Reactions where oxidation and reduction happen simultaneously